The present invention relates in general to microfluidic systems and to electrophoretic separation analysis systems and to fluid sample loading systems.
Microchip electrophoresis separation technology has developed separation and detection systems which take only minutes to analyze many samples in parallel. Such rapid high density microcapilary separation and detection array systems have been microfabricated, for example, on glass microplates.
High throughput separation and detection systems require not only high speed separation and data collection, but they also require fast and efficient systems for introducing small amounts of samples and reagents into the analysis system. A problem with existing systems is that as the newer microplate technologies require considerably less time to perform parallel separation and detection, the actual time taken to load such arrays is becoming the time bottleneck for system operation.
Current methods of loading such arrays, such as using serial or parallel pipette loaders are time consuming, and only serial loading is well suited to loading non-orthogonal arrays of wells. Although robotic fluid loading systems are useful, they are complex, expensive, and generally not well adapted to load non-orthogonal arrays. Other current loading systems such as systems using long flexible glass capillaries suffer from the disadvantage of clogging very easily, and problems of achieving uniform transfer rates.
In one preferred aspect, the present invention provides a system adapted to simultaneously transfer a plurality of small volumes of liquid samples from a first well geometry to a second well geometry. In preferred aspects, the present invention can be used to transfer small volumes of liquid samples from an orthogonal array format of sample wells to another array format using microfluidic channels in a layered substrate structure.
In optional preferred aspects, the array format into which the samples are transferred may comprise wells disposed around the outer perimeter of a circular microfabricated plate wherein the wells are connected to a radial array of separation channels in an electrophoretic separation microchannel system. Such a radial array of separation channels offers advantages because they are easily laid out, and they can be scanned by a novel confocal radial fluorescence detector, as disclosed in U.S. Pat. No. 6,100,535, incorporated herein in its entirety for all purposes.
An advantage of the present system is that a plurality of fluid samples can be transferred simultaneously from a first sample well format to a second sample well format, providing a fast system for loading a plurality of fluid samples into an analysis system simultaneously. A second advantage of the present system is that the various fluid samples can be loaded into the various wells in the receiving microplate in precisely metered volumes at precisely the same rate and at precisely the same time. This is particularly advantageous when loading a plurality of different samples into discrete electrophoretic separation channels such that the samples can then all be electrophoretically separated at the same time. This in turn permits multiplexing of various anode, cathode or waste reservoirs in the separation microplate. Multiplexing of the various anode, cathode or waste reservoirs in the separation microplate advantageously reduces the number of reservoirs which need to be formed on the surface of the separation microplate.
In preferred aspects, the analysis system into which the samples are simultaneously loaded comprises a microcapillary electrophoretic separation system, which may optionally comprise a plurality of microchannels etched onto a top surface of a micromachined plate or wafer. It is to be understood, however, that the present invention is directed to simultaneously loading samples into any array of wells in any analysis or detection system. As such, sample wells in systems other than microcapilary electrophoretic separation systems may also be loaded by the present invention.
In optional preferred aspects, the xe2x80x9clayered substrate structurexe2x80x9d of the present invention comprises two or more wafers placed one on top of the other. These wafers may be made of glass, silicon or plastics, or other suitable materials.
In preferred aspects of the invention, the small volumes of liquid samples transferred or loaded by the present invention comprise fluid samples in the microliter to sub-microliter range.
Advantageously, the present system can be fabricated with excellent control of exact device geometry, thereby providing microfluidic channels having very small lengths and volumes such that only a very small sample volume is required in these microfluidic channels. An advantage of the present invention is that, due to the small dimensions of the system, the potential for sample absorption into the walls of the microchannels is minimized, as is the potential for sample or reagent volume being used up in filling the microchannels of the present system.
A further advantage of the present invention is that a plurality of the present systems can be made by batch processing, whereby many wafer plates are made in parallel. This makes wafer plate stacks easily replaceable in the case of a clog or failure, and also allows for the production of multiple designs. Moreover, it is easy to fabricate a variety of different transfer devices designed for loading different array formats in accordance with the present invention.
A further advantage of the present invention is that its novel manifold design permits it to accept various different sample loading systems having different designs of channels thereon, further increasing system flexibility.